Adult meccano?
Rexroth (mostly the aluminium profile struts) and the components that bolt to it.
http://www.boschrexroth.com/en/xc/products/product_groups/assembly_technology_1/index
And yeah, more than £40. But if you want to prototype a mars rover chassis…
http://www.astrium.eads.net/en/news2/all-you-want-to-know-about-bridget.html
Good shout IA.
I use this stuff a lot at work and it can be used for all sorts of bike related stuff. Wheel truing jigs, free stands, wall mount stands….
http://www.kjnltd.co.uk/ Are good, they will even cut it for you if you do not have the facilities.
Well and truly Meccano for grown ups!